Improving temperature capacity of tnm-based tial alloys

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Liu, Bo (2019). Improving temperature capacity of tnm-based tial alloys. University of Birmingham. Ph.D.

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Abstract

A TNM alloy based on the nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (at%) is the typical third-generation alloy which has been commercially tested on aero-engines. As an alloy for the production of LPT blades, the alloy must meet the requirements of forging small parts as blade preforms. The amount of stored heat energy is low during the process of extruding small diameter roads and rolling thin sheets. Thus, it is necessary that the selected alloy comes with a fine-grained, globular and isotropic casting microstructure. To realise the above microstructure, a new Ti-44.4Al-4Nb-1Mo-0.8B (at%) has been designed and heat treated. The solidification pathway of Ti-44.4Al-4Nb-1Mo-0.8B (TNM-0.8B) follows L+β→β and avoids the peritectic solidification of L+β→α, that is, the concentration of Al is defined in the range of 39%-45%. The addition of β phase stabilising elements Nb and Mo can stabilise the β phase by extending the β phase region to higher Al contents. Also, the strength and creep resistance of TiAl alloys are significantly enhanced at high temperature, meanwhile, the corrosion and pitting resistance of TiAl alloys in some acid and neutral chloride solutions are also increased at various temperatures. With the addition of the element B, the grain size of TiAl alloys is refined significantly.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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